The present invention relates to controlled release plant nutrients and crop protection compositions and particularly, to fertilizers showing a release in a certain period of time, and to a method for producing controlled release compositions.
Encapsulations and coats of plant nutrients are the major methods for providing controlled release nutrients. Water-soluble nutrients encapsulated in water insoluble coatings are released at controlled rates. Sulfur coated fertilizers are widely used for controlled release purposes as disclosed in U.S. Pat. No. 3,342,577.
Polymer encapsulation is another popular method to make controlled release fertilizers (CRF). Examples of these polymer encapsulation methods are found in U.S. Pat. No. 4,657,576 (use of a dicyclopentadiene based resin to encapsulate water-soluble fertilizers); U.S. Pat. Nos. 6,039,781; 4,711,659, 4,804,403, and 4,969,947 (urethane based coatings of fertilizers); U.S. Pat. Nos. 5,851,251 and 6,001,147 (urea and urethane based fertilizer coatings); and U.S. Pat. No. 5,803,946 and European patent 1,043,295 A2 (interpenetrating polymer coating process that includes urethane with other resins). In order to overcome the shortcomings of sulfur coatings, processes using additional layers of polymer coatings are disclosed in U.S. Pat. Nos. 5,219,465 and 5,466,274. The use of a wax as a sealant for sulfur coated urea is disclosed in U.S. Pat. No. 5,478,375. A polymeric coating process based on sulfonated ethylene-propylene-diene terpolymers is disclosed in U.S. Pat. No. 5,429,654. An epoxy resin based coating is disclosed in U.S. Pat. No. 5,698,002.
While the above noted efforts provide promise, there is still a need in the industry for inexpensive and high quality CRFs to expand the application of these fertilizers.
Accordingly, one object of the present invention is to provide controlled release fertilizers coated with organic or organic/inorganic composite materials.
Another object of this invention is to provide controlled release fertilizer products that have high resistance to attrition during handling and applications.
Another object of the invention is to provide a method to produce such controlled release fertilizer products economically and practically.
These and other objects have been satisfied by the discovery of a method for coating fertilizers to provide controlled release properties comprising forming a self assembly of amphiphilic molecules having a hydrophilic portion and a hydrophobic portion, wherein the hydrophilic portion is proximal relative to the fertilizer and the hydrophobic portion is distal to the fertilizer, the self assembly forming a multilayer that provides a hydrophobic barrier to block water vapor and water from contacting the fertilizer.